http://freebsdwiki.net/index.php?action=history&feed=atom&title=GeomGeom - Revision history2026-05-23T18:05:04ZRevision history for this page on the wikiMediaWiki 1.18.0http://freebsdwiki.net/index.php?title=Geom&diff=10959&oldid=prevJimbo at 12:07, 3 January 20092009-01-03T12:07:45Z<p></p>
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<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>     GEOM on the other hand does not care in which order things are done, the</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>     GEOM on the other hand does not care in which order things are done, the</div></td></tr>
<tr><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>     only restriction is that cycles in the graph will not be allowed.</div></td><td class='diff-marker'> </td><td style="background: #eee; color:black; font-size: smaller;"><div>     only restriction is that cycles in the graph will not be allowed.</div></td></tr>
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</table>Jimbohttp://freebsdwiki.net/index.php?title=Geom&diff=6870&oldid=prev212.36.8.135 at 11:46, 5 September 20062006-09-05T11:46:36Z<p></p>
<p><b>New page</b></p><div> The GEOM framework provides an infrastructure in which "classes" can per-<br />
form transformations on disk I/O requests on their path from the upper<br />
kernel to the device drivers and back.<br />
<br />
Transformations in a GEOM context range from the simple geometric dis-<br />
placement performed in typical disk partitioning modules over RAID algo-<br />
rithms and device multipath resolution to full blown cryptographic pro-<br />
tection of the stored data.<br />
<br />
Compared to traditional "volume management", GEOM differs from most and<br />
in some cases all previous implementations in the following ways:<br />
<br />
o GEOM is extensible. It is trivially simple to write a new class of<br />
transformation and it will not be given stepchild treatment. If<br />
someone for some reason wanted to mount IBM MVS diskpacks, a class<br />
recognizing and configuring their VTOC information would be a trivial<br />
matter.<br />
<br />
o GEOM is topologically agnostic. Most volume management implementa-<br />
tions have very strict notions of how classes can fit together, very<br />
often one fixed hierarchy is provided for instance subdisk - plex -<br />
volume.<br />
<br />
Being extensible means that new transformations are treated no differ-<br />
ently than existing transformations.<br />
<br />
Fixed hierarchies are bad because they make it impossible to express the<br />
intent efficiently. In the fixed hierarchy above it is not possible to<br />
mirror two physical disks and then partition the mirror into subdisks,<br />
instead one is forced to make subdisks on the physical volumes and to<br />
mirror these two and two resulting in a much more complex configuration.<br />
GEOM on the other hand does not care in which order things are done, the<br />
only restriction is that cycles in the graph will not be allowed.</div>212.36.8.135